Coherent spread-spectrum coded waveforms in synthetic aperture image formation

Abstract

Techniques, systems, and devices are disclosed for synthetic aperture ultrasound imaging using spread-spectrum, wide instantaneous band, coherent, coded waveforms. In one aspect, a method includes synthesizing a composite waveform formed of a plurality of individual orthogonal coded waveforms that are mutually orthogonal to each other, correspond to different frequency bands and including a unique frequency with a corresponding phase; transmitting an acoustic wave based on the composite waveform toward a target from one or more transmitting positions; and receiving at one or more receiving positions acoustic energy returned from at least part of the target corresponding to the transmitted acoustic waveforms, in which the transmitting and receiving positions each include one or both of spatial positions of an array of transducer elements relative to the target and beam phase center positions of the array, and the transmitted acoustic waveforms and the returned acoustic waveforms produce an enlarged effective aperture.

What is claimed is: 
     
       1. A method for producing acoustic waveforms, comprising:
 producing a composite waveform that includes of a plurality of individual coded waveforms each corresponding to distinct frequency bands, such that each of the individual coded waveforms includes a unique frequency with a corresponding phase, wherein the producing of the composite waveform includes:
 generating a set of random numbers, 
 selecting individual composite digital codes based on the generated set of random numbers, wherein each of the individual composite digital codes correspond to the individual coded waveforms in digital format, and 
 forming the composite waveform from the selected individual coded waveforms; 
 
 producing and transmitting a composite acoustic beam, based on the generated composite waveform, toward a material of interest, wherein the transmitting includes selecting one or more transducing elements of a transducer array of an acoustic imaging device to transduce the plurality of individual coded waveforms of the produced composite waveform into a plurality of corresponding acoustic waveforms that form the composite acoustic beam, wherein the composite acoustic beam is transmitted from one or more transmitting positions of the transducer array relative to the material of interest; 
 receiving, at one or more receiving positions relative to the material of interest, returned acoustic waveforms that are returned from at least part of the material of interest corresponding to at least some transmitted acoustic waveforms that form the composite acoustic beam, wherein the receiving includes selecting at least some of the transducing elements of the transducer array to receive the returned acoustic waveforms, 
 wherein transmitted acoustic waveforms and received returned acoustic waveforms produce an enlarged effective aperture of the acoustic imaging device. 
 
     
     
       2. The method of  claim 1 , further comprising:
 processing the received returned acoustic waveforms to produce an image containing information of the material of interest. 
 
     
     
       3. The method of  claim 1 , wherein the transmitting includes generating drive signals corresponding to the composite waveform to drive the transducer elements of the transducer array to form the composite acoustic beam. 
     
     
       4. The method of  claim 1 , further comprising:
 producing and transmitting a second composite acoustic beam toward the material of interest, wherein the transmitting the second composite acoustic beam includes selecting one or more additional transducer elements of the transducer array to transduce a second plurality of individual orthogonal coded waveforms into a second plurality of corresponding acoustic waveforms to form the second composite acoustic beam to be transmitted toward the material of interest, 
 wherein the first composite acoustic beam and the second composite acoustic beam produce an enlarged non-real aperture when transmitted toward the material of interest. 
 
     
     
       5. The method of  claim 1 , wherein the transmitting positions and the receiving positions each include one or both of (i) spatial positions of the transducer array relative to the target and (ii) beam phase center positions of the transducer array. 
     
     
       6. The method of  claim 1 , wherein the generated set of random numbers includes random amplitudes or both random amplitudes and random phases. 
     
     
       7. The method of  claim 1 , further comprising:
 storing the selected individual composite digital codes in memory of one or more computer devices. 
 
     
     
       8. The method of  claim 1 , wherein the selected individual coded waveforms include coherent waveforms. 
     
     
       9. The method of  claim 1 , wherein the selected individual coded waveforms include frequency-coded waveforms, phase-coded waveforms, or frequency-coded and phase-coded waveforms. 
     
     
       10. The method of  claim 1 , wherein at least one of the selected individual coded waveforms that form the composite waveform includes two or more amplitudes, two or more phases, or two or more amplitudes and two or more phases. 
     
     
       11. The method of  claim 1 , wherein at least some of the selected individual coded waveforms that form the composite waveform are individually amplitude weighted, individually phase weighted, or both individually amplitude weighted and individually phase weighted, thereby providing at least one of steering, focus, or forming of the composite acoustic beam. 
     
     
       12. The method of  claim 1 , wherein at least some of the individual coded waveforms include individual orthogonal coded waveforms that are mutually orthogonal to each other. 
     
     
       13. A system for producing acoustic waveforms, comprising:
 a computing device comprising a processor and a memory and configured to produce a composite waveform that includes a plurality of individual coded waveforms each corresponding to distinct frequency bands, such that each of the individual coded waveforms includes a unique frequency with a corresponding phase, wherein the computing device is operable to produce the composite waveform by: generating a set of random numbers, selecting individual composite digital codes based on the generated set of random numbers, wherein each of the individual composite digital codes correspond to the individual coded waveforms in digital format, and forming the composite waveform from the selected individual coded waveforms; 
 a digital to analog (D/A) converter, in communication with the computing device, to convert the individual coded waveforms that form the composite waveform from the digital format to an analog format as an analog composite waveform; 
 an acoustic imaging device comprising an array of transducer elements, in communication with the D/A converter, to obtain the analog composite waveform and transmit a composite acoustic beam toward a material of interest, wherein the array of transducer elements are operable to receive returned acoustic waveforms that are returned from at least part of the material of interest corresponding to at least some transmitted acoustic waveforms that form the composite acoustic beam, 
 wherein the array of transducer elements are configured to transmit the composite acoustic beam by selecting one or more of the transducing elements of the array to transduce the plurality of individual coded waveforms of the produced composite waveform into a plurality of corresponding acoustic waveforms that form the composite acoustic beam, such that the composite acoustic beam is transmitted from one or more transmitting positions of the array relative to the material of interest, 
 wherein the array of transducer elements are configured to receive the returned acoustic waveforms by selecting at least some of the transducing elements of the array to receive the returned acoustic waveforms, 
 wherein transmitted acoustic waveforms and received returned acoustic waveforms produce an enlarged effective aperture of the acoustic imaging device; and 
 an analog to digital (A/D) converter, in communication with the array of transducer elements, to convert the received returned acoustic waveforms received by the array of transducer elements from an analog format to a digital format as a received composite waveform comprising information of the material of interest. 
 
     
     
       14. The system of  claim 13 , wherein the array of transducers are configured to acoustically couple to a receiving volume containing the material of interest, and wherein a transmission of the composite acoustic beam by the array of transducer elements includes generating drive signals corresponding to the composite waveform that drive the transducer elements of the array to create and propagate the composite acoustic beam in the receiving volume and toward the material of interest. 
     
     
       15. The system of  claim 13 , wherein the computing device includes a controller unit and a user interface unit in communication with the controller unit, wherein the controller unit is configured to process the received composite waveform to produce an image of at least part of the material of interest and display the image via the user interface. 
     
     
       16. The system of  claim 13 , wherein a generated set of random numbers generatable by the computing device includes random phases. 
     
     
       17. The system of  claim 13 , wherein a generated set of random numbers generatable by the computing device includes random amplitudes or both random amplitudes and random phases. 
     
     
       18. The system of  claim 13 , wherein the computing device is configured to store the selected individual composite digital codes in the memory. 
     
     
       19. The system of  claim 13 , wherein the selected individual coded waveforms include coherent waveforms. 
     
     
       20. The system of  claim 13 , wherein the selected individual coded waveforms include frequency-coded waveforms, phase-coded waveforms, or frequency-coded and phase-coded waveforms. 
     
     
       21. The system of  claim 13 , wherein at least one of the selected individual coded waveforms that form the composite waveform includes two or more amplitudes, two or more phases, or two or more amplitudes and two or more phases. 
     
     
       22. The system of  claim 13 , wherein at least some of the individual coded waveforms include individual orthogonal coded waveforms that are mutually orthogonal to each other.